Retaining wall

Retaining walls are relatively rigid walls used for supporting the soil mass laterally so that the soil can be retained at different levels on the two sides. Retaining walls are structures designed to restrain soil to a slope that it would not naturally keep to (typically a steep, near-vertical or vertical slope). They are used to bound soils between two different elevations often in areas of terrain possessing undesirable slopes or in areas where the landscape needs to be shaped severely and engineered for more specific purposes like hillside farming or roadway overpasses. A retaining wall that retains soil on the backside and water on the frontside is called a seawall or a bulkhead.

Stone Retaining wall
A gravity-type stone retaining wall

Definition

A retaining wall is a structure designed and constructed to resist the lateral pressure of soil, when there is a desired change in ground elevation that exceeds the angle of repose of the soil.[1]

A basement wall is thus one kind of retaining wall. But the term usually refers to a cantilever retaining wall, which is a freestanding structure without lateral support at its top.[2] These are cantilevered from a footing and rise above the grade on one side to retain a higher level grade on the opposite side. The walls must resist the lateral pressures generated by loose soils or, in some cases, water pressures.[3]

Terminology

Every retaining wall supports a "wedge" of soil. The wedge is defined as the soil which extends beyond the failure plane of the soil type present at the wall site, and can be calculated once the soil friction angle is known. As the setback of the wall increases, the size of the sliding wedge is reduced. This reduction lowers the pressure on the retaining wall.[4]

The most important consideration in proper design and installation of retaining walls is to recognize and counteract the tendency of the retained material to move downslope due to gravity. This creates lateral earth pressure behind the wall which depends on the angle of internal friction (phi) and the cohesive strength (c) of the retained material, as well as the direction and magnitude of movement the retaining structure undergoes.

Lateral earth pressures are zero at the top of the wall and – in homogenous ground – increase proportionally to a maximum value at the lowest depth. Earth pressures will push the wall forward or overturn it if not properly addressed. Also, any groundwater behind the wall that is not dissipated by a drainage system causes hydrostatic pressure on the wall. The total pressure or thrust may be assumed to act at one-third from the lowest depth for lengthwise stretches of uniform height.[5]

Unless the wall is designed to retain water, It is important to have proper drainage behind the wall in order to limit the pressure to the wall's design value. Drainage materials will reduce or eliminate the hydrostatic pressure and improve the stability of the material behind the wall. Drystone retaining walls are normally self-draining.

As an example, the International Building Code requires retaining walls to be designed to ensure stability against overturning, sliding, excessive foundation pressure and water uplift; and that they be designed for a safety factor of 1.5 against lateral sliding and overturning.[6]

Types

Retaining Wall Type Function
Various types of retaining walls

Gravity

Gravity Walls
Construction types of gravity retaining walls

Gravity walls depend on their mass (stone, concrete or other heavy material) to resist pressure from behind and may have a 'batter' setback to improve stability by leaning back toward the retained soil. For short landscaping walls, they are often made from mortarless stone or segmental concrete units (masonry units).[7] Dry-stacked gravity walls are somewhat flexible and do not require a rigid footing.

Earlier in the 20th century, taller retaining walls were often gravity walls made from large masses of concrete or stone. Today, taller retaining walls are increasingly built as composite gravity walls such as: geosynthetics such as geocell cellular confinement earth retention or with precast facing; gabions (stacked steel wire baskets filled with rocks); crib walls (cells built up log cabin style from precast concrete or timber and filled with granular material).[8]

Cantilevered

Cantilevered retaining walls are made from an internal stem of steel-reinforced, cast-in-place concrete or mortared masonry (often in the shape of an inverted T). These walls cantilever loads (like a beam) to a large, structural footing, converting horizontal pressures from behind the wall to vertical pressures on the ground below. Sometimes cantilevered walls are buttressed on the front, or include a counterfort on the back, to improve their strength resisting high loads. Buttresses are short wing walls at right angles to the main trend of the wall. These walls require rigid concrete footings below seasonal frost depth. This type of wall uses much less material than a traditional gravity wall.

Sheet piling

Spundwand
Sheet pile wall

Sheet pile retaining walls are usually used in soft soil and tight spaces. Sheet pile walls are driven into the ground and are composed of a variety of material including steel, vinyl, aluminum, fiberglass or wood planks. For a quick estimate the material is usually driven 1/3 above ground, 2/3 below ground, but this may be altered depending on the environment. Taller sheet pile walls will need a tie-back anchor, or "dead-man" placed in the soil a distance behind the face of the wall, that is tied to the wall, usually by a cable or a rod. Anchors are then placed behind the potential failure plane in the soil.

Bored pile

Bored pile retaining walls are built by assembling a sequence of bored piles, proceeded by excavating away the excess soil. Depending on the project, the bored pile retaining wall may include a series of earth anchors, reinforcing beams, soil improvement operations and shotcrete reinforcement layer. This construction technique tends to be employed in scenarios where sheet piling is a valid construction solution, but where the vibration or noise levels generated by a pile driver are not acceptable.

Anchored

Anchored wall
Anchored wall in the mountainous region of Rio de Janeiro state, Brazil

An anchored retaining wall can be constructed in any of the aforementioned styles but also includes additional strength using cables or other stays anchored in the rock or soil behind it. Usually driven into the material with boring, anchors are then expanded at the end of the cable, either by mechanical means or often by injecting pressurized concrete, which expands to form a bulb in the soil. Technically complex, this method is very useful where high loads are expected, or where the wall itself has to be slender and would otherwise be too weak. Soil-nailed walls (soil reinforced in place with steel and concrete rods).

Alternative retaining techniques

Soil nailing

Soil nailing is a technique in which soil slopes, excavations or retaining walls are reinforced by the insertion of relatively slender elements – normally steel reinforcing bars. The bars are usually installed into a pre-drilled hole and then grouted into place or drilled and grouted simultaneously. They are usually installed untensioned at a slight downward inclination. A rigid or flexible facing (often sprayed concrete) or isolated soil nail heads may be used at the surface.

Soil-strengthened

A number of systems exist that do not consist of just the wall, but reduce the earth pressure acting directly on the wall. These are usually used in combination with one of the other wall types, though some may only use it as facing, i.e., for visual purposes.

Gabion meshes

This type of soil strengthening, often also used without an outside wall, consists of wire mesh "boxes", which are filled with roughly cut stone or other material. The mesh cages reduce some internal movement and forces, and also reduce erosive forces. Gabion walls are free-draining retaining structures and as such are often built in locations where ground water is present. However, management and control of the ground water in and around all retaining walls is important.

Mechanical stabilization

Mechanically stabilized earth, also called MSE, is soil constructed with artificial reinforcing via layered horizontal mats (geosynthetics) fixed at their ends. These mats provide added internal shear resistance beyond that of simple gravity wall structures. Other options include steel straps, also layered. This type of soil strengthening usually needs outer facing walls (S.R.W.'s – Segmental Retaining Walls) to affix the layers to and vice versa.[9]

The wall face is often of precast concrete units[7] that can tolerate some differential movement. The reinforced soil's mass, along with the facing, then acts as an improved gravity wall. The reinforced mass must be built large enough to retain the pressures from the soil behind it. Gravity walls usually must be a minimum of 50 to 60 percent as deep or thick as the height of the wall, and may have to be larger if there is a slope or surcharge on the wall.

Cellular confinement systems (geocells) are also used for steep earth stabilization in gravity and reinforced retaining walls with geogrids. Geocell retaining walls are structurally stable under self- weight and externally imposed loads, while the flexibility of the structure offers very high seismic resistance.[10] The outer fascia cells of the wall can be planted with vegetation to create a green wall.

See also

References

  1. ^ Ching, F. D., Faia., R., S., & Winkel, P. (2006). Building Codes Illustrated: A Guide to Understanding the 2006 International Building Code (2 ed.). New York, NY: Wiley.
  2. ^ Ambrose, J. (1991). Simplified Design of Masonry Structures. New York: John Wiley and Sons, Inc. pp. 70–75. ISBN 0471179884.
  3. ^ Crosbie, M. & Watson, D. (Eds.). (2005). Time-Saver Standards for Architectural Design. New York, NY: McGraw-Hill.
  4. ^ (2011) Commercial Installation Manual for Allan Block Retaining Walls (p. 13)
  5. ^ Terzaghi, K. (1934). Large Retaining Wall Tests. Engineering News Record Feb. 1, March 8, April 19.
  6. ^ 2006 International Building Code Section 1806.1.
  7. ^ a b "Segmental Retaining Walls". National Concrete Masonry Association. Archived from the original on 2008-03-04. Retrieved 2008-03-24.
  8. ^ Terzaghi, K. (1943). Theoretical Soil Mechanics. New York: John Wiley and Sons.
  9. ^ JPG image. geostone.com
  10. ^ Leshchinsky, D. (2009). "Research and Innovation: Seismic Performance of Various Geocell Earth-retention Systems". Geosysnthetics. 27 (4): 46–52.

Further reading

  • Bowles, J.,(1968). Foundation Analysis and Design, McGraw-Hill Book Company, New York
  • Ching, F. D., Faia., R., S., & Winkel, P. (2006). Building Codes Illustrated: A Guide to Understanding the 2006 International
  • Crosbie, M. & Watson, D. (Eds.). (2005). Time-Saver Standards for Architectural Design. New York, NY: McGraw-Hill.
2001 Daytona 500

The 2001 Daytona 500, the 43rd running of the event, was the first race of the 2001 NASCAR Winston Cup Series schedule. It was held on February 18, 2001 at Daytona International Speedway in Daytona Beach, Florida, consisting of 200 laps and 500 miles on the 2.5-mile (4 km) asphalt tri-oval. The race was the first ever Winston Cup telecast shown by the Fox network, which had received broadcasting rights along with NBC at the end of the previous season, replacing the two former NASCAR broadcasting channels CBS and ESPN. Bill Elliott won the pole and Michael Waltrip, in his first race in the No. 15 car for Dale Earnhardt, Inc., won the race. This was the first Winston Cup victory of his career, coming in his 463rd start, the longest wait for a first win. His teammate Dale Earnhardt Jr. finished second and Rusty Wallace finished third.

On the final lap, a major accident was triggered by Sterling Marlin losing control of his car and taking out Dale Earnhardt Sr and Ken Schrader in a head-on collision with the outside retaining wall in turn 4. Three cars were involved in the crash, which killed Earnhardt instantly. The race was also marred by an 18-car pile-up on lap 173 that began when Ward Burton made contact with Robby Gordon, sending Tony Stewart flipping twice down the backstretch. After Earnhardt's death (as well as other notable deaths of other drivers in other NASCAR national touring series in the previous season), NASCAR implemented rigorous safety improvements in later seasons.

Ashwell War Memorial

Ashwell War Memorial is a war memorial cross in the village of Ashwell in North Hertfordshire. The memorial was designed by Sir Edwin Lutyens and unveiled in 1922, one of 15 war crosses designed by Lutyens to similar designs erected between 1920 and 1925. It is a Grade II listed building.

A parish war memorial committee was formed in Ashwell in 1919, chaired by a local brewer Wolverley Attwood Fordham. The committee requested design proposals from the architects Sir Reginald Blomfield, and Sir Edwin Lutyens, and from a local building firm, Tappers, before deciding to commission a cross designed by Lutyens. The memorial was constructed built by Holland, Hannen & Cubitts, who also built Lutyens' Cenotaph in Whitehall, at a cost of £557, including a fee of nearly £43 for Lutyens.

The memorial is located on the east side of Ashwell village, to the west side of the junction of Lucas Lane and Station Road. It comprises a tapering Portland stone war cross, standing on a square plinth and podium, on a circular stone base of only two steps rather than the usual three, surrounded by grass. The memorial is raised above the road junction by a stone retaining wall with a flight of six steps. The cross bears several inscriptions: to the front "IN HONOUR OF THE MEN OF / ASHWELL WHO FOUGHT IN THE / GREAT WAR AND IN LOVING / MEMORY OF THOSE WHO FELL / OUR GLORIOUS DEAD" then some names then the inscription "THEIR NAME LIVETH FOR EVERMORE". The south side bears the date "1914" and more names, and the north side bears the date "1919" and yet more names. Further names were inscribed on the podium later to record the war dead from the Second World War. It bears 42 names in all.

The memorial was unveiled on 4 December 1921 by the Lord Lieutenant of Hertfordshire Thomas Brand, 3rd Viscount Hampden. It became a Grade II listed building in November 1984.

Beekman Place

Beekman Place is a small street located on the east side of Manhattan, New York, in the neighborhood of Turtle Bay. Running from north to south for two blocks, the street is situated between the eastern end of 51st Street and Mitchell Place, where it ends at a retaining wall above 49th Street, overlooking the glass apartment towers at 860 and 870 United Nations Plaza, just north of the United Nations Headquarters complex. "Beekman Place" also refers to the residential neighborhood that surrounds the street itself. It is named after the Beekman family, who were influential in New York City's development.

Bridgehouses railway station

Bridgehouses railway station was the terminal station of the Sheffield, Ashton-under-Lyne and Manchester Railway from its opening in 1845 until the opening of the Wicker Arches, a 660-yard (600 m) long viaduct across the Don Valley, which supported the new Sheffield Victoria opened on 15 September 1851. On 1 January 1847 a ½-mile connecting line to the Wicker station of the Midland Railway had been constructed in order to increase goods traffic and enable wagon transfers. This short steeply graded line, enclosed within a tunnel for almost its entire length was known locally as the Fiery Jack.By this time the railway operating company had become the Manchester, Sheffield and Lincolnshire Railway, which in 1899 became the Great Central Railway. From 1851 Bridgehouses became the company's terminal for goods and cattle traffic. It remained open for freight until 1965.

The station was approached by a ramp from Nursery Street and on the opposite corner a public house was built. Originally named "The Manchester Railway Hotel" its frontage was damaged in the Sheffield Flood of 1864 and was rebuilt (look at the alignment to the main building). It was renamed "The Manchester Hotel" and in spring 2006, after a short period of closure, it became "The Harlequin", taking the name from a recently demolished pub which stood a short distance away in Johnson Street.

Part of the station site is now used as a car park and part of the retaining wall along Nursery Street has been demolished to make way for the northern section of Sheffield's Inner Ring Road. It has been suggested that this retaining wall might have contained stones from Sheffield Castle.

Before the building of the "Borough Bridge", which carries Corporation Street across the River Don to reach Nursery Street, passenger access to the station from the city area was by a footbridge, depicted by an unknown artist, c. 1840. On the night of 11 March 1864, when the waters of the Great Sheffield flood poured over the bridge, a vast quantity of timber and debris came down with the force of a battering ram, and carried the footbridge away. A successor to this bridge is still standing adjacent to the new bridge which carries the Inner Ring Road over the River Don, although it is in need of restoration.

The terminal was the subject of a BBC local television documentary "Engines must not enter the potato siding" which contained vintage film and memories from former railway workers and which was broadcast in November 1969 at the time of the rationalisation of goods traffic in the Sheffield area and the opening of the new Sheffield Freight Terminal in Brightside Lane. This was adjacent to the site of the former Midland Railway locomotive sheds and yard. The potato siding was situated high above the road and had a wooden floor, fine for wagons and vans but as the title says, not locomotives.

Bulkhead (barrier)

A bulkhead is a retaining wall, such as a bulkhead within a ship or a watershed retaining wall. It may also be used in mines to contain flooding.

Coastal bulkheads are most often referred to as seawalls, bulkheading, or riprap revetments. These manmade structures are constructed along shorelines with the purpose of controlling beach erosion. Construction materials commonly used include wood pilings, commercially developed vinyl products, large boulders stacked to form a wall, or a seawall built of concrete or another hard substance.

Coastal property owners typically seek to develop bulkheads in an attempt to slow large landslide erosion caused by wave action. Studies over recent decades have resulted in public awareness as to potential negative effects that bulkheads may bring to beaches and the interconnected habitat areas of fish, plants, and birds. Many states have enacted laws to protect beaches to allow for future use of the beaches, as well as protect these natural habitats.

Carlton D. Wall House

The Carlton D. Wall House is a Frank Lloyd Wright designed home in Plymouth, Michigan. It is one of Wright's more elaborate Usonian homes. In 1941, recently married Mr. and Mrs. Carlton David Wall, who were Wright's youngest clients, approached Wright to design a house for them after Carlton Wall studied Wright's architecture in college.Its form is a series of hexagons radiating from a central chimney or service core without any true right angles, with many different wings off it for a nursery, terrace, guest room and carport. The cypress and brick house came to be known as Snowflake because of the hexagonal patterns created by the diamond grid design. This was the first use of Wright's modular diamond structure in Michigan, a technique he used elsewhere when incorporating a house into a hillside.A massive brick retaining wall supports a dramatic terrace. Floor to ceiling windows, doors without mullions, and corner windows are used throughout the house. This brings the "outside in", which is the case in all Wright houses. From 1943-44, Milton Horn collaborated with Wright on a wood relief mural for the house. In 1947, a 1,000-square-foot (93 m2) bedroom wing was added to accommodate the Walls' growing family. It is located to the west of the original house.

Snowflake was purchased by Tom Monaghan (founder of Domino's Pizza) in 1983, and it was used on a rotating basis by executives of his corporation. It was to be part of Mr. Monaghan's Frank Lloyd Wright Study Center. In the late 1980s it was sold to the current owners who use it as their personal residence.

Central Croydon railway station

Central Croydon railway station in Croydon, England, was a largely unsuccessful venture by the London Brighton and South Coast Railway to bring trains closer to the centre of Croydon, as East Croydon station was deemed too far from the busy town centre. It originally opened in 1868 and closed in 1871: it then reopened in 1886, before closing permanently in 1890. Its site was used for the building of Croydon Town Hall, erected in 1892–1896.

Elham railway station

Elham railway station is a disused railway station on the Elham Valley Railway which served the village of Elham in Kent and the surrounding villages. Situated to the east of Elham the clapboard station was opened in 1887. In 1931 the line was singled and one platform was closed. Regular passenger services were withdrawn on 1 December 1940 when the line was taken over for military use. In 1946 the line was reopened for goods traffic but a year later this service ceased when the station was officially closed. After closure the station building was demolished but one platform still exists forming a retaining wall of a garden for a house now built on the station site.

Fineview (Pittsburgh)

Fineview is a neighborhood on Pittsburgh, Pennsylvania's North Side. It has zip codes of both 15212 and 15214, and has representation on Pittsburgh City Council by the council member for District 6 (North Shore and Downtown neighborhoods) and District 1 (North Central neighborhoods).

Fineview was known to older generations as Nunnery Hill. Its modern name derives from the expansive views of downtown Pittsburgh. The most famous of these views is from the Fineview Overlook at the corner of Catoma and Meadville streets.

For older generations, this neighborhood was well known for its locally famous streetcar line (#21 Fineview), and for its incline, known as the Nunnery Hill Incline. This incline was one of two in the city that had a curve in it (the other was the Knoxville Incline on the South Side). The incline started at the present-day intersection of Henderson Street and Federal Street. The curve was located in the area of Henderson Street and Jay Street. The incline ended at the top of the hill, along Meadville Street. The old retaining wall that was built for the incline can still be seen running up the side of Henderson Street. This route ran from 1908 to April 30, 1966.

Headwall

In physical geography and geology the headwall of a glacial cirque is its highest cliff. The term has been more broadly used to describe similar geomorphic features of non-glacial origin consisting of a concave depression with convergent slopes typically of 65 percent or greater forming the upper end of a drainage valley.In civil engineering, a headwall is a small retaining wall placed at the inlet or outlet of a stormwater pipe or culvert.

North Kelvinside

North Kelvinside (also referred to as North Kelvin or Maryhill, Scottish Gaelic: Cealbhainn a Tuath) is a residential district of the Scottish city of Glasgow.

It is usually regarded as a subdistrict of Maryhill, sharing its G20 postcode, as well as its House of Commons electoral constituency prior to incorporation into Glasgow North in 2005. However, North Kelvinside was never a part of Maryhill Police Burgh prior to its incorporation into Glasgow in 1912 and the area is markedly different socially and architecturally.

North Kelvinside was originally part of a country estate, which became enveloped by the surrounding city. As a result, many buildings date from the early twentieth century. It is located on the northern edge of Glasgow's west end and its southern boundary is marked by the River Kelvin. It is close to the Glasgow Botanic Gardens, the former BBC building on Queen Margaret Drive, and in the vicinity of the University of Glasgow, although all are actually outwith the North Kelvinside area itself. Being close to Glasgow University many students and academics live in the area.

Kelvinside House was the property of Lord Provost Sir James Campbell, and was located in the area that is now North Kelvinside. It was there that his son, the future Prime Minister Sir Henry Campbell-Bannerman was born 1836.

North Kelvinside is not directly north of the more upmarket area Kelvinside, which is mainly located to the west. Rather, the area is so named because it is located on the north bank of the River Kelvin. The housing consists mainly of tenements, although there are also some grander villa-type buildings, converted Victorian townhouses, pre-industrial cottages and a small, well-maintained (now mainly ex-)council estate. The area has a reputation for being quiet and tranquil, despite its central location. Unusually, it is impossible to fully traverse the district by car in any direction, due in part to its extremely hilly topography, and to a system of road-blocks designed to combat ratrunning.

Architecturally significant buildings in the area include the Kelvin Stevenson Memorial Church (by J. J. Stevenson, 1898) and Gillespie, Kidd & Coia's St. Charles Parish Church (1959), noted for its hyperbolic paraboloid concrete roof and Stations of the Cross sculptures by Benno Schotz. Another local landmark is Alexander "Greek" Thomson's Sixty Steps (1872). Contemporary published sources suggest that the steps, associated retaining wall and the original Queen Margaret Bridge were actually part of John E. Walker's co-ordinated civil engineering works of 1869/1870 to the designs of Ritchie Rodger C.E. in preparation for the development of the suburb.North Kelvinside also contains the pub where the famous 'balcony' scene in the film Trainspotting was shot, the beautiful Kelvin walkway along the banks of the eponymous river, linking Kelvingrove Park and the Botanic Gardens, and the tiny North Star cafe, a bohemian hang-out. The area has relatively few retail or leisure facilities, but is within easy walking distance of the numerous shops, pubs and restaurants on Great Western and Byres Roads.

Famous current or former residents include the actor Robbie Coltrane, director Lynne Ramsay, screenwriter and playwright Peter McDougall, members of the rock band Teenage Fanclub, TV interior designers Justin Ryan and Colin McAllister, Ian Davidson MP and former Maryhill MP, Maria Fyfe.

There was a North Kelvinside Secondary School that served most of the Maryhill district of Glasgow. However, the school was closed and the vast majority of the pupil's transferred to Cleveden Secondary School in the Kelvindale area on the other side of the River Kelvin to the west. Former famous pupils include actor Robert Carlyle and 80's pop-star Jimmy Somerville as well as Janis Sharp mother of Gary McKinnon.

The area is served by North Kelvinside Parish Church, a Church of Scotland congregation which was made famous after World War II, by the work and writing of its minister Rev Tom Allan, particularly his book The Face of My Parish. However, in recent years, the church building was demolished, leaving only the halls which are now in poor condition. The congregation has also been in sharp decline and is currently uniting with the nearby Ruchill Parish Church.

Just south of the area is Hillhead, which forms the heart of Glasgow's west end, and to the north is Maryhill. To the west are Kelvindale and Kelvinside, and to the east Firhill and Woodside.

The district, along with Firhill and Murano Street Student Village, is served by North Kelvin Community Council.

Precast concrete

Precast concrete is a construction product produced by casting concrete in a reusable mold or "form" which is then cured in a controlled environment, transported to the construction site and lifted into place ("tilt up"). In contrast, standard concrete is poured into site-specific forms and cured on site. Precast stone is distinguished from precast concrete using a fine aggregate in the mixture, so the final product approaches the appearance of naturally occurring rock or stone. More recently expanded polystyrene is being used as the cores to precast wall panels. This is lightweight and has better thermal insulation.

Precast is used within exterior and interior walls. By producing precast concrete in a controlled environment (typically referred to as a precast plant), the precast concrete is afforded the opportunity to properly cure and be closely monitored by plant employees. Using a precast concrete system offers many potential advantages over onsite casting. Precast concrete production can performed on ground level, which helps with safety throughout a project. There is greater control over material quality and workmanship in a precast plant compared to a construction site. The forms used in a precast plant can be reused hundreds to thousands of times before they have to be replaced, often making it cheaper than onsite casting when looking at the cost per unit of formwork.There are many different types of precast concrete forming systems for architectural applications, differing in size, function, and cost. Precast architectural panels are also used to clad all or part of a building facades or free-standing walls used for landscaping, soundproofing, and security walls, and some can be prestressed concrete structural elements. Stormwater drainage, water and sewage pipes, and tunnels make use of precast concrete units.

To complete the look of the four precast wall panel types — sandwich, plastered sandwich, inner layer and cladding panels — many surface finishes are available. Standard cement is white or grey, though different colors can be added with pigments or paints. The color and size of aggregate can also affect the appearance and texture of concrete surfaces. The shape and surface of the precast concrete molds have an effect on the look: The mold can be made of timber, steel, plastic, rubber or fiberglass, each material giving a unique finish.

Queen's Gardens, Croydon

The Queen's Gardens are a small area of urban gardens in the centre of Croydon, South London. They are bordered by Croydon Town Hall, Bernard Weatherill House, the site of the former Taberner House, Park Lane and Katharine Street.

In their present form (and under their present name), the gardens and their central fountain were opened by Queen Elizabeth II in 1983. The area had previously consisted of the smaller Town Hall Gardens, and the site of Croydon's police station. The Town Hall Gardens had originally been laid out in the 1890s on the site of the disused spur railway line leading to Croydon Central station.

The gardens now comprise areas of lawn with standard trees, a central fountain with benches, and a sunken garden area with formal flower beds and trees exploiting the former track bed and station wall complete with original railings on top. Situated just across from Croydon's register office, the gardens are popular for wedding photographs. A subway exits the park under Park Lane into an underground car park and across to the Fairfield Halls; the gardens are well-used as a path between Council offices and to the underpass.

The cancelled Park Place development featured proposals to radically alter the Queen's Gardens, with a more formal and modern planting style, an ice rink, space for performances and entrance into the Park Place shopping centre. The gardens remain part of the Croydon Vision 2020 regeneration plan.

Seawall

A seawall (or sea wall) is a form of coastal defense constructed where the sea, and associated coastal processes, impact directly upon the landforms of the coast. The purpose of a sea wall is to protect areas of human habitation, conservation and leisure activities from the action of tides, waves, or tsunamis. As a seawall is a static feature it will conflict with the dynamic nature of the coast and impede the exchange of sediment between land and sea. The shoreline is part of the coastal interface which is exposed to a wide range of erosional processes arising from fluvial, aeolian and terrestrial sources, meaning that a combination of denudational processes will work against a seawall.The coast is generally a high-energy, dynamic environment with spatial variations over a wide range of timescales. The coast is exposed to erosion by rivers and winds as well as the sea, so that a combination of denudational processes will work against a sea wall.

Because of these persistent natural forces, sea walls need to be maintained (and eventually replaced) to maintain their effectiveness.

The many types of sea wall in use today reflect both the varying physical forces they are designed to withstand, and location specific aspects, such as local climate, coastal position, wave regime, and value of landform. Sea walls are hard engineering shore-based structures which protect the coast from erosion. But various environmental problems and issues may arise from the construction of a sea wall, including disrupting sediment movement and transport patterns. Combined with a high construction cost, this has led to an increasing use of other soft engineering coastal management options such as beach replenishment.

Sea walls may be constructed from various materials, most commonly reinforced concrete, boulders, steel, or gabions. Other possible construction materials are: vinyl, wood, aluminium, fibreglass composite, and large biodegrable sandbags made of jute and coir. In the UK, sea wall also refers to an earthen bank used to create a polder, or a dike construction.

St Andrew's Church, Portland

St Andrew's Church is a ruined church located above Church Ope Cove on the Isle of Portland, Dorset, England. St Andrew's was Portland's first parish church and remained as such until the mid-18th century. It is now one of the island's prime historical sites, and is a Grade II* Listed Building and a Scheduled Monument. The southern retaining wall of the churchyard is also Grade II Listed, as are three remaining churchyard monuments, approximately 7 metres south of the church.

Thornton railway station

Thornton railway station was a station on the Keighley-Queensbury section of the Queensbury Lines which ran between Keighley, Bradford and Halifax via Queensbury. The station served the village of Thornton, West Yorkshire, England from 1878 to 1955.

The station had an island platform and was very close to the 300-yard (270 m) 20 arch Thornton viaduct which spans the Pinch Beck valley. It opened for passengers in 1878 and closed in 1955.

The viaduct, closed off for many years, was reopened in 2008 as part of the Great Northern Walking Trail after it had been safety checked and the former railway bed was sealed. No other parts of the former large station building remain. The site is occupied by Thornton Primary School (previously Royd Mount Middle School) since 1977. The original goods platform and a large retaining wall are still visible and have been incorporated into the school's grounds design. The viaduct is a grade II listed building, and is unusual in that it has an 'S' shape to accommodate the natural contours of the valley. It is in a picturesque location that has remained unchanged since its construction. The final trip by train over the viaduct was in 1966, by a goods train.The original 'Thornton' platform sign was a large concrete affair, some 16 feet (5 m) long. This is on display at the Industrial Museum at Eccleshill on the outskirts of the city of Bradford.

Wall

A wall is a structure that defines an area, carries a load, or provides shelter or security. There are many kinds of walls, including:

Defensive walls in fortifications

Walls in buildings that form a fundamental part of the superstructure or separate interior rooms, sometimes for fire safety

Retaining walls, which hold back dirt, stone, water, or noise sound

Walls that protect from oceans (seawalls) or rivers (levees)

Permanent, solid fences

Border barriers between countries

Brick wall

Precast wall

Stone wall

Glass wall (only when most of the wall, in smaller amounts it is called a window)

Doors are mobile walls on hinges which open to form a gateway

Warner Apartment Building

The Warner Apartment Building was an historic building located on the east side of Davenport, Iowa, United States. Dr. Fay L. Warner, a dentist, had the structure built in 1900 and lived here himself until 1908. A relative of his, Fred Warner, lived here in later years and managed the building. The three-story brick structure was one of the most distinguished apartment blocks in Davenport. The building featured a picturesque façade that was typical of Victorian era architecture. The round arch entrances were below ogee-arched moldings. At the top was a deep corbelled cornice frieze. The five sections of the main façade were articulated by full-height octagonal bays. The building was also banded by flat and projecting string courses. The structure was on a raised lot and had a low, stone retaining wall at the sidewalk. It was listed on the National Register of Historic Places in 1983, and has subsequently been demolished.

Whitehouse, New Jersey

Whitehouse is an unincorporated community located within Readington Township in Hunterdon County, New Jersey, United States. The community lies along the Jersey Turnpike, just west of Mechanicsville.

In 1722, Abraham Van Horne purchased 490 acres (2.0 km2) in Readington along the Rockaway Creek. There, he built a grist mill and saw mill. Around 1750, he built a white plastered wall tavern on the creek where the Jersey Turnpike crossed (this is now the corner of Washington Street and U.S. Route 22). The tavern began to be referred to as the "White House" by travellers. The village, which sprang up to the east of the tavern also carried this name. Stones from the original tavern can be seen along the retaining wall of the Daughters of the American Revolution cemetery, where the tavern once stood. The community of White House stretched along the Jersey Turnpike (now Route 22 and Old Route 28), which was the main street. The settlement included taverns, stores, grist mills, an academy, a Dutch Reformed Church and numerous houses.Nearby Whitehouse Station, which also indirectly took the name from the tavern, was not built up until 1848 when an extension of the Somerville and Easton Railroad was built.

The Whitehouse-Mechanicsville Historic District, which includes historic places in both Whitehouse and Mechanicsville, was added to the National Register of Historic Places on March 17, 2015.

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